In the North American railroad industry, bottom dumping gondola cars and open top hopper cars are frequently used. In more recent times standards for contamination of lading have risen, such that it may be desirable to take steps to prevent traces of lading from one car load being transported with the car when it is filled with subsequent lading.
Quite separately, where the lading may be corrosive, or may tend to attract or retain moisture, it may be desirable to take steps to discourage accumulation of lading on upward facing surfaces adjacent to the discharge section of the car.
It may also be desirable to take such steps without giving rise to unintended consequences in terms of the structural integrity, durability, service life or performance of the car over its operating life.